Monday, February 26, 2007

Moneyball fans already know about this, but I thought this weekend's NY Times article on OPS and its derivative GPA (gross production average), was a helpful primer on the statistic. It's pretty interesting that OPS, even for its advances relative to the traditional batting average statistic, might be better utilized using a GPA translation due to its more-familiar scale:

Most stat-savvy baseball folks sense that on-base percentage is more valuable, perhaps drastically so, because it better recognizes the importance of not making outs. David Wright of the Mets agreed last week, saying: “You can always make things happen when you get on base. When I think of slugging percentage, I think of sitting back for the three-run homer, which might not happen.”

[Victor Wang, who published an article on the relative value of OBP and slugging average in a SABR journal,] wasn’t the first researcher to look into exactly how much more valuable on-base percentage may be. The Hardball Times, a statistics-oriented think tank out of the Baseball Prospectus mold, recently identified the same factor of 1.8 and started weighting O.P.S. [on-base percentage plus slugging] accordingly. Better yet, one last simple step — dividing by four — put this new measure (called Gross Production Average) on the comfortably familiar scale of batting average, with figures generally ranging from .200 (horrible) to .265 (roughly average) to around .360 (superior). It’s a language that most fans speak....

O.P.S. appeared on the scene in the 1970s, with on-base and slugging percentages being added rather than multiplied (which everyone agreed was more accurate) solely because it was simpler. O.P.S. is old enough that The New York Times published weekly top 10 leaders as early as 1985. But again, that didn’t last long. Even today, with O.P.S. the most accepted nontraditional statistic, fans still have trouble intuitively sensing if an .850 O.P.S. is good or bad.

The salvation for Gross Production Average could be how it translates a better O.P.S. into the customary .200-to-.360 scale. G.P.A.’s .300 hitters are just about as elite as traditional ones: Last year, 38 batters hit .300 in batting average, while 32 hit .300 in G.P.A. They are just not the same hitters, which is the entire point.

So there you have it, GPA = [(OBP * 1.8) + SLG] / 4, then adjusted for ballpark factor. Maybe GPA seems more intuitive since it fits the old scale; or maybe it's because we subconsciously have been trained to care about GPAs since high school.

In 2006, the leading GPA on the Dodgers was JD Drew, 22nd in the majors, with a .309 GPA. Of current Dodgers, Nomar Garciaparra was 36th in the majors, with a .299 GPA.